Filamentous fungi are known to secrete various enzyme proteins to the outside of the cell body. By using such a property of filamentous fungi, from old times, various filamentous fungi, in particular, filamentous fungi such as of the genus Aspergillus, have been widely used in brewing field for producing bean paste, soy sauce, sake, and the like, and in production of enzyme preparations. As a result of breeding for a long time for enhancing the production ability of extracellular enzyme, a strain capable of producing several tens grams of enzyme proteins per litter of a culture solution has been obtained.
On the other hand, with a recent application of a genetic recombination technology, various proteins can be produced. In the production of enzyme proteins using recombinant bacteria, as a means for producing a large amount of target enzymes, promoters having stronger transcription ability have been searched to be used from the viewpoint that enhancement of the transcription ability of genes may lead to high production. From such a viewpoint, hitherto, various promoters derived from filamentous fungi have been isolated and protein production systems using such promoters have been reported. For example, a promoter of the amylase gene of Aspergillus oryzae (see, for example, Japanese Patent Unexamined Publication No. S62-272988 and Biotechnology, 5,368 (1987)), a promoter of the glucoamylase gene of Aspergillus nigar (see, for example, Biotechnology, 6, 1419 (1988)), and the like, have been isolated and used. In addition, enhancement of the ability of promoters by introducing an enhancer or modifying a regulation region, and the like, has been carried out. According to the production of gene products depending upon the ability of promoters as mentioned above, the production ability has been more efficiently enhanced as compared with the enhancement of ability by a conventional breeding method. However, in order to increase an absolute amount of the production of extracellular enzyme proteins, further improvement in breeding of host strains by applying a conventional breeding method has been carried out.